Overall price range, I'm hoping to be under or around $650 before tax. But if theres really good reason to spend more, I'd consider it.

The new parts I need for the HTP should cost roughly $300 (65 for case, 60 for HD, 45 for PSU, 130 for mobo)

For the upgrades for my main, I'll be looking at another $300-350.
150 for a mobo (recommendations are welcome...not sure what the best for OCing is at that range.)
120 for cpu if i get i3 540. Is there any value in getting an i5, or will a well oc'd i3 be good?
60 bucks or so for 4gb of ram.